Adhesive, adhesive sheet, multi-layered adhesive sheet, and production method for electronic part

ABSTRACT

A multi-layered adhesive sheet  100 , includes: a substrate film  106 , an adhesive layer  103  formed by coating an adhesive having a specific composition onto this substrate film  106 , and a die attachment film  105  laminated on the adhesive layer  103 . The multi-layered adhesive sheet  100  employing an adhesive having this specific composition has superior retention of die chip  108  during the dicing of silicon wafer  101 , allows the die attachment film  105  and adhesive layer  103  to be easily peeled apart during a pick-up operation of the die chip  108 , and prevents poor adhesion during the bonding of die chip  108  to lead frame  111.

TECHNICAL FIELD

The present invention relates to an adhesive, an adhesive sheetemploying the adhesive, a multi-layered adhesive sheet employing theadhesive sheet, and a production method for an electronic part employingthe multi-layered adhesive sheet.

BACKGROUND ART

As a production method for an electronic part such as an IC, a method ofmanufacturing a chip with a semiconductor wafer or insulating substrateas a base material, picking-up the chip, fixing it to a lead frame orthe like via an adhesive agent or the like and sealing it with resin orthe like to form an electronic part, is known. As the production methodfor the electronic part, a method of forming an electronic partsassembly by forming a circuit pattern on an insulating substrate or asemiconductor wafer of gallium arsenide, silicon or the like, attachingthe electronic parts assembly to an adhesive sheet, then separating andcutting (dicing) it into individual chips after fixing it to a ringframe, elongating (expansion) the sheet when necessary, picking-up thechips, fixing the chips to the lead frame and the like via an adhesiveagent, is widely performed (refer to Non-Patent Document 1).

A method of employing a multi-layered adhesive sheet (die attachmentfilm all-in-one sheet) providing the combined functions of an adhesiveagent that fixes a chip to a lead frame or the like, with that of anadhesive sheet for dice cutting, has been proposed. The die attachmentfilm all-in-one sheet is an integrated multi-layered adhesive sheet ofan adhesive sheet and a die attachment film. By employing the dieattachment film all-in-one sheet in the production of an electronicpart, a coating process of an adhesive agent can be omitted therefrom.

When compared to a method using an adhesive agent, the die attachmentfilm all-in-one sheet is advantageous in that it is capable ofcontrolling thickening of the adhered portions or preventing oozing. Adie attachment film all-in-one sheet is employed in the production ofsemiconductor packages, such as a chip size package, a stack package,and a system-in-a-package (refer to Patent Documents 1 to 3).

As the adhesive of the adhesive sheet employed during the dicing of theelectronic parts assembly, a method of employing a radiationpolymerizable compound having at least two unsaturated bonds with acopolymer of a (meth)acrylic ester and hydroxyl group-containingpolymerizable monomer, is known (refer to Patent Document 4).

As an acrylic adhesive, one containing a urethane acrylate oligomer andacrylic compound having various functional groups, having a Tg (glasstransition temperature) of −60° C. to −30° C., and having a weightaverage molecular weight of 200,000 or more, is known (refer to PatentDocument 5).

Patent Document 1: Japanese Patent Application Laid-Open Publication No.H02-248064;Patent Document 2: Japanese Patent Application Laid-Open Publication No.H08-053655;

Patent Document 3: Japanese Patent Application Laid-Open Publication No.2004-186429; Patent Document 4: Japanese Patent No. 3410202;

Patent Document 5: Japanese Patent Application Laid-Open Publication No.H11-293201; andNon-Patent Document 1: T. Ozawa et al., Adhesive Properties ofUltraviolet Curable Adhesive Tape for Semiconductor Processing(I)-Interpretation via Rheological Viewpoint, Furukawa Review, No. 106,pp. 31-36, Furukawa Electric Co. Ltd. (July, 2000).

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

However, along with the higher integration of semiconductor parts, chipsizes have gotten considerably thinner, and cases in which pick-upoperations of chips have become difficult after dicing have increased.Moreover, since the compatibility between an adhesive sheet and a dieattachment film is comparatively higher than the compatibility betweenan adhesive sheet and a semiconductor wafer, there are instances wherethis leads to an insufficient reduction in adhesion even after exposureto an electron beam/ultraviolet rays, an inferiority in the easiness ofpeeling at the time of pick-up, and pick-up defects.

The present invention was achieved in view of the abovementionedproblems, and as such provides an adhesive, an adhesive sheet employingthe adhesive, a multi-layered adhesive sheet employing the adhesivesheet and a production method for an electronic part employing themulti-layered adhesive sheet, allowing the adhesive sheet and the dieattachment film to be easily peeled apart during pick-up, which inallows for a chip pick-up operation to be easily performed after dicing.

Means for Solving the Problems

According to the present invention, an adhesive is provided whichcontains a (meth)acrylic acid ester polymer, a urethane acrylateoligomer having at least four vinyl groups, and a silicone graftpolymer.

According to the adhesive, it prevents pick-up defects in the chipsbecause it allows for the easy peeling apart between a die attachmentfilm and an adhesive layer of the adhesive sheet when picking-up chipsafter dicing. Moreover, along with being superior in chip retentionduring dicing, contamination of the die attachment film from a fineadhesive residue is also low. Accordingly, this adhesive may bepreferably employed in the adhesive layer of a die attachment filmall-in-one sheet.

Moreover, the abovementioned adhesive is one embodiment of the presentinvention; and an adhesive sheet employing the adhesive of the presentinvention, a multi-layered adhesive sheet employing the adhesive sheet,and a production method for an electronic part employing themulti-layered adhesive sheet, and the like, also embody similartechnical features, and achieve similar effects.

EFFECTS OF THE INVENTION

According to the present invention, because an adhesive having aspecific composition is employed, it allows for easy peeling of a chipduring a pick-up operation, while also allowing for favorable chipretention during dicing. Furthermore, because a die attachment film isnot contaminated after dicing, the occurrence of poor adhesion between achip attached to the die attachment film and a lead frame can beprevented.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view describing a structure of amulti-layered adhesive sheet of one embodiment of the present invention;

FIG. 2 is a photograph for describing chip retention; and

FIG. 3 is a schematic diagram for describing a pick-up property.

EXPLANATION OF THE REFERENCE NUMERALS

-   100 multi-layered adhesive sheet-   101 silicon wafer-   102 ring frame-   103 adhesive layer-   104 dicing blade-   105 die attachment film-   106 substrate film-   107 incision-   108 die chip-   110 adhesive sheet-   111 lead frame

PREFERRED MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described withreference to the drawings. However, in cases where the same constituentsare appended with the same reference numerals in each of the drawings,duplicate descriptions thereof will be omitted.

Description of the Terms

In the present specification, “monomer” refers to the monomersthemselves or the structures derived from monomers. “Portion” and“percent” of the present specification refers to a mass basis, exceptwhere specifically described. In the present specification, a(meth)acryloyl group is a generic term for an acryloyl group and amethacryloyl group. The same also holds true for a compound including a(meth) such as (meth)acrylic acid and the like, in which the genericterm is for a compound that does not include “meth” in the name and acompound that does include “meth” in the name. The number of functionalgroups within a urethane acrylate oligomer refers the number of vinylgroups per single urethane acrylate oligomer molecule.

Brief Overview of the Embodiments

FIG. 1 is a cross-sectional view describing a structure of amulti-layered adhesive sheet of the present embodiment.

As shown in FIG. 1(1), the multi-layered adhesive sheet 100 of thepresent embodiment (die attachment film all-in-one sheet) includes: asubstrate film 106, an adhesive layer 103 formed by coating thebelow-described adhesive onto this substrate film 106, and a dieattachment film 105 laminated on this adhesive layer 103.

An adhesive sheet 110 refers to a sheet formed by combining theabovementioned substrate film 106 with the adhesive layer 103 formed bycoating below-described adhesive onto the substrate film 106.Specifically, a multi-layered pressure-sensitive sheet 100 includes: anadhesive sheet 110, and a die attachment film 105 laminated on theadhesive layer 103 side of this adhesive sheet 110.

In addition, the abovementioned adhesive layer 103 is formed by beingcoated on the substrate film 106 with an adhesive containing a(meth)acrylic acid ester polymer, a urethane acrylate oligomer having atleast four vinyl groups, and a silicone graft polymer.

The multi-layered pressure-sensitive sheet 100 employing adhesive havingthe abovementioned composition allows for easy peeling of the dieattachment film 105 and the adhesive layer 103 of the adhesive sheet 110during a pick-up operation of a die chip 108. Moreover, because theabove-described multi-layered adhesive sheet 100 is also superior inchip retention, the peeling of the die chip 108 during dicing(hereinafter, referred to as “chip scattering”) can be prevented.

Moreover, a production method for an electronic part employing themulti-layered adhesive sheet 100, allows for the pick-up of the die chip108 with the die attachment film 105 attached to a rear surface of thedie chip 108 after the dicing of a silicon wafer 101, and the die chip108 to be mounted and bonded as is on a lead frame 111 or the like. Insuch cases, since the contamination of the die attachment film 105 froma fine adhesive residue is low, the occurrence of poor adhesion can beprevented.

Adhesive Layer

The adhesive layer 103 is composed of an adhesive containing a(meth)acrylic acid ester polymer, a urethane acrylate oligomer having atleast four vinyl groups, and a silicone graft polymer. Theabove-described adhesive layer 103 composed of such an adhesive allowsfor easy peeling of the die attachment film 105 from the adhesive layer103 during the pick-up operation of the die chip 108. Moreover, the chipretention during dicing is excellent, and the contamination of the dieattachment film 105 is also low.

A (meth)acrylic acid ester polymer is a polymer in which a (meth)acrylicacid ester monomer is polymerized. Moreover, a (meth)acrylic acid esterpolymer may also include a vinyl compound monomer other than a(meth)acrylic acid ester monomer.

As a monomer of a (meth)acrylic acid ester, butyl (meth)acrylate,2-butyl (meth)acrylate, t-butyl (meth)acrylate, pentyl (meth)acrylate,octyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, nonyl (meth)acrylate,decyl (meth)acrylate, lauryl (meth)acrylate, methyl (meth)acrylate,ethyl (meth)acrylate, isopropyl (meth)acrylate, tridecyl (meth)acrylate,myristyl (meth)acrylate, cetyl (meth)acrylate, stearyl (meth)acrylate,cyclohexyl (meth)acrylate, isoboronyl (meth)acrylate, dicyclopentanyl(meth)acrylate, benzyl (meth)acrylate, methoxyethyl (meth)acrylate,ethoxyethyl (meth)acrylate, butoxymethyl (meth)acrylate, andethoxy-n-propyl (meth)acrylate, 2-hydroxyethyl (meth)acrylate,2-hydroxypropyl (meth)acrylate, and 2-hydroxybutyl (meth)acrylate may beexemplified.

As the vinyl compound monomer, one having at least one of functionalgroup selected from a hydroxyl group, a carboxyl group, an epoxy group,an amide group, an amino group, a methylol group, a sulphonic acidgroup, a sulfamic acid group, and a phosphite ester group may bepreferably employed.

As the vinyl compound monomer having a hydroxyl group, a vinyl alcoholmay be exemplified.

As the vinyl compound monomer having a carboxyl group, (meth)acrylicacid, crotonic acid, maleic acid, anhydrous maleic acid, itaconic acid,fumaric acid, acrylamido-N-glycoljc acid, and cinnamic acid may beexemplified.

As the vinyl compound monomer having an epoxy group, allyl glycidylether and (meth)acrylic acid glycidyl ether may be exemplified.

As the vinyl compound monomer having an amide group, (meth)acrylamidemay be exemplified.

As the vinyl compound monomer having an amino group, N,N-dimethylaminoethyl (meth)acrylate may be exemplified.

As the vinyl compound monomer having a methylol group, N-methylolacrylamide may be exemplified.

A production method for the (meth)acrylic acid ester polymer may employemulsion polymerization, solution polymerization, or the like. Anacrylic rubber that is capable of being manufactured by emulsionpolymerization is preferable, so as to allow for the adhesive sheet 110and the die attachment film 105 to be easily peeled apart after exposureto radiation.

The urethane acrylate oligomer having at least four vinyl groups(hereinafter, also referred to as “urethane acrylate oligomer”) is notspecifically limited, so long as it is a (meth)acrylate oligomer havinga urethane bond in the molecule and having at least four vinyl groups.

Although a production method for a urethane acrylate oligomer is notparticularly limited in any way, reacting a (meth)acrylate compoundcontaining a hydroxyl group and a plurality of (meth)acrylate groupswith a compound (for example, a diisocyanate compound) having aplurality of isocyanate groups may be exemplified as a method foryielding a urethane acrylate oligomer. Moreover, a compound (forexample, a diisocyanate compound) having a plurality of isocyanategroups may be added in excess to a polyol oligomer having a plurality ofhydroxyl terminal groups, reacted therewith to yield an oligomer havinga plurality of isocyanate terminal groups, then further reacted with a(meth)acrylate compound containing a hydroxyl group and plurality of(meth)acrylate groups to yield a urethane acrylate oligomer.

As the (meth)acrylate compound containing hydroxyl group and pluralityof (meth)acrylate groups, hydroxypropylated trimethylolpropanetriacrylate, pentaerythritol triacrylate,dipentaerythritol-hydroxy-penta acrylate, bis(pentaerythritol)-tetraacrylate, tetramethylol methane triacrylate, glycidol-diacrylate, or acompound substituting all or some of acrylate groups of these compoundswith the methacrylate group may be exemplified.

As an isocyanate having a plurality of isocyanate groups, aromaticisocyanate, alicyclic isocyanate, and aliphatic isocyanate may beexemplified. Among isocyanates having a plurality of isocyanate groups,aromatic isocyanate or an alicyclic isocyanate may be preferablyemployed. As the form of an isocyanate compound, monomers, dimmers andtrimers exist, with a trimer being preferably employed.

As an aromatic diisocyanate, tolylene diisocyanate, 4,4-diphenylmethanediisocyanate, and xylylene diisocyanate may be exemplified.

As an alicyclic diisocyanate, isophorone diisocyanate, andmethylenebis(4-cyclohexyl isocyanate) may be exemplified.

As an aliphatic diisocyanate, hexamethylene diisocyanate, and trimethylhexamethylene diisocyanate may be exemplified.

As the polyol oligomer having a plurality of hydroxyl terminal groups,poly(propylene oxide)diol, poly(propylene oxide)triol, copoly(ethyleneoxide-propylene oxide)diol, poly(tetramethylene oxide)diol, ethoxylatedbisphenol A, ethoxylated bisphenol S spiroglycol, caprolactone modifieddiol, and carbonate diol may be exemplified.

When the number of vinyl groups included in the urethane acrylateoligomer is less than four, there are instances where the die attachmentfilm 105 and the adhesive layer 103 are not easily peeled apart afterexposure to radiation, and there is a reduction in the pick-upproperties of the die chip 108. On the other hand, while the number ofvinyl groups included in the urethane acrylate oligomer is notparticularly limited in any way, considering the availability and themanufacturing costs thereof, it is preferable that no more than 15 vinylgroups are included therein.

Although the compounding amount of the urethane acrylate oligomer is notparticularly limited in any way, at least 20 parts by mass to no morethan 200 parts by mass with respect to 100 parts by mass of(meth)acrylic acid ester polymer is preferable. When the compoundingamount of the urethane acrylate oligomer having at least four vinylgroups is less than 20 parts by mass, there are instances where theadhesive sheet 110 and the die attachment film 105 are not easily peeledapart after exposure to ultraviolet rays and/or radiation, and problemsoccur with the pick-up properties of the die chip 108. Moreover, whencompounded in excess of 200 parts by mass, along with instances wherepick-up defects are caused by the scooping up of adhesive during dicing,there are instances where a fine residue is generated from a reactionresidue, and where poor adhesion occurs when heat is applied during themounting of the die chip 108 having the die attachment film 105 attachedthereto on the lead frame 111.

The silicone graft polymer is not particularly limited in any manner, solong as is one in which a monomer having a vinyl group at an end of asilicone molecule chain (hereinafter, referred to as “siliconemacromonomer”) is polymerized. Thus, a homopolymer of a siliconemacromonomer or a copolymer of another vinyl compound and a siliconemacromonomer may be exemplified. The silicone macromonomer that ispreferably employed is a compound having a vinyl group such as a(meth)acryloyl group or a styryl group at an end of a silicone moleculechain (refer to Patent Document 6).

As the abovementioned other vinyl compound, a (meth)acrylic monomer thatis highly compatible with another polymer compounded into the adhesiveis preferable. Employing such a highly compatible (meth)acrylic monomerkeeps the entire adhesive homogeneous.

The (meth)acrylic monomer is not particularly limited in any particularmanner, and thus alkyl (meth)acrylate, hydroxyalkyl (meth)acrylate,modified hydroxy (meth)acrylate, and (meth)acrylic acid may beexemplified. However, a hydroxyalkyl (meth)acrylate or a modifiedhydroxy (meth)acrylate is preferably employed due to their reactivity,in order to prevent fine residues referred to as “particles”.

As the alkyl (meth)acrylate, methyl (meth)acrylate, ethyl(meth)acrylate, n-propyl (meth)acrylate, n-butyl (meth)acrylate,isobutyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl(meth)acrylate, lauryl (meth)acrylate, stearyl (meth)acrylate, andisobornyl (meth)acrylate, and hydroxyalkyl (meth)acrylate may beexemplified.

As the hydroxyalkyl (meth)acrylate, hydroxyethyl (meth)acrylate,hydroxypropyl (meth)acrylate, and hydroxybutyl (meth)acrylate may beexemplified.

As the modified hydroxy (meth)acrylate, ethylene oxide modified hydroxy(meth)acrylate, and lactone modified hydroxy (meth)acrylate may beexemplified.

Although the ratio of silicone macromonomeric units within the siliconegraft polymer is not particularly limited in any manner, at least 15parts by mass to no more than 50 parts by mass of siliconemacromonomeric units with respect to 100 parts by mass of the siliconegraft polymer is preferable. When the content of the siliconemacromonomeric units is less than 15 parts by mass, there are instanceswhere the adhesive sheet 110 and the die attachment film 105 are noteasily peeled apart after exposure to radiation, and the pick-upproperties of the die chip 108 degrades. Moreover, when the content ofthe silicone macromonomeric units exceeds 50 parts by mass, thereinstances where it bleeds out onto a surface of the adhesive layer 103,the die attachment film 105 is contaminated, and poor adhesion occurswhen heat is applied during the mounting of the die chip 108 having thedie attachment film 105 attached thereto on top of the lead frame 111.

Although the compounding amount of the silicone graft polymer is notparticularly limited in any way, at least 0.1 parts by mass to no morethan 10 parts by mass with respect to 100 parts by mass of (meth)acrylicacid ester polymer is preferable. When the compounding amount of thesilicone graft polymer is less than 0.1 parts by mass, there areinstances where the adhesive sheet 110 and the die attachment film 105are not easily peeled apart after exposure to ultraviolet rays and/orradiation, and problems occur with the pick-up properties of the diechip 108. Furthermore, when the compounding amount of the silicone graftpolymer exceeds 10 parts by mass, there are instances where initialadhesion is low, and it is peeled from ring frame 102 during dicing.

A tackifying resin may also be added to the adhesive in order to controladhesiveness. The tackifying resin is not particularly limited in anyway, and thus rosin resin, rosin ester resin, terpene resin, terpenephenol resin, phenol resin, xylene resin, cumarone resin,cumarone-indene resin, styrene resin, aliphatic petroleum resin,aromatic petroleum resin, aliphatic aromatic copolymer petroleum resin,alicyclic hydrocarbon resin, and a modified product thereof, aderivative thereof, or a hydrogenated product thereof may beexemplified.

Although the compounding amount of the tackifying resin is notparticularly limited in any manner, no more than 200 parts by mass ispreferable, with no more than 30 parts by mass being optimal withrespect to 100 parts by mass of (meth)acrylic acid ester polymer.

Various additives such a curing agent, a polymerization initiator, asoftening agent, an anti-oxidizing agent, a bulking agent, a ultravioletabsorber, a photostabilizer, and the like may also be added to theadhesive.

A thickness of the adhesive layer 103 is preferably at least 1 μm, witha thickness of at least 2 μm being especially preferable. Furthermore,the thickness of the adhesive layer 103 is preferably no more than 100μm, with a thickness of no more than 40 μm being especially preferable.When the thickness of the adhesive layer 103 is thinner than 1 μm, alongwith a reduction in adhesion and a reduction in chip retention duringdicing, there are instances where peeling occurs between the ring frame102 and the multi-layered adhesive sheet 100. Moreover, when thethickness of the adhesive layer 103 surpasses 100 μm, the adhesionbecomes too strong, and there are instances where pick-up defects occur.

Adhesive Sheet

The adhesive sheet 110, which is produced by coating an adhesive onsubstrate film 106, is composed of substrate film 106 and adhesive layer103 formed on this substrate film 106. The thickness of the substratefilm 106 is preferably at least 30 μm, and even more preferably at least60 μm. Furthermore, the thickness of the substrate film 106 ispreferably no more than 300 μm, and even more preferably no more than200 μm.

The raw material of the substrate film 106 is not particularly limitedin any manner, and thus polyvinyl chloride, polyethylene terephthalate,ethylene-vinyl acetate copolymer, ethylene-acrylic acid-acrylic esterfilm, ethylene-ethylacrylate copolymer, polyethylene, polypropylene,ethylene-acrylic acid copolymer, and ionomer resin in which anethylene-(meth)acrylic acid copolymer or ethylene-(meth)acrylicacid-(meth)acrylic acid ester copolymer or the like is crosslinked witha metal ion, may be exemplified. A mixture, a copolymer and amulti-layered film or the like of these resins may be employed in thesubstrate film 106.

Preferably, an ionomer resin is employed as raw material of thesubstrate film 106. Even among ionomer resins, using an ionomer resin inwhich a copolymer having ethylene units, (meth)acrylic acid units and(meth)acrylic acid alkyl ester units is crosslinked with metal ions suchas Na⁺, K⁺ and Zn²⁺, prevents the generation of beard shaped cuttingdebris, and thus it is preferably employed.

A forming method of the substrate film 106 is not particularly limitedin any manner, and thus a calendar forming method, a T-die extrusionmethod, an inflation method, and a casting method may be exemplified.

In order to prevent the electrostatic charge during the peeling of thedie attachment film 105, an antistatic treatment may be executed on asurface of the substrate film 106 that makes contact and/or does notmake contact with the die attachment film 105. An anti-electrostaticagent may be introduced into the resin. The antistatic treatment mayemploy an anti-electrostatic agent such as a quaternary amine saltmonomer.

As the quaternary amine salt monomer, quaternary dimethylaminoethyl(meth)acrylate chloride, quaternary diethylaminoethyl (meth)acrylatechloride, quaternary methylethylaminoethyl (meth)acrylate chloride,quaternary p-dimethylaminostyrene chloride, and quaternaryp-diethylaminostyrene chloride may be exemplified, with quaternarydimethylaminoethyl (meth)acrylate chloride being preferably employed.

A method of use of the anti-electrostatic agent and the lubricant is notparticularly limited in any manner, for example, an adhesive may becoated onto one side of the substrate film 106, and the lubricant and/orthe anti-electrostatic agent may be coated onto a rear surface thereof;or the lubricant and/or the anti-electrostatic agent may be formed intoa sheet by kneading it into the resin of the substrate film.

The die attachment film 105 is laminated onto the adhesive layer 103 onone side of the substrate film 106, which allows the other surface ofthe substrate film 106 to be an embossed surface with an average surfaceroughness (Ra) of at least 0.3 μm to no more than 1.5 μm. By placing theembossed surface on a machine table side of an expansion device (notshown), the substrate film 106 can be easily expanded via an expansionprocess after dicing.

The lubricant can be applied to a surface of the substrate film 106 thatdoes not make contact with the die attachment film 105, and thelubricant can be kneaded into the substrate film 106, in order improvethe expansion properties after dicing.

The lubricant is not particularly limited in any particular manner, solong as the material reduces the coefficient of friction between theadhesive sheet 110 and the expansion device (not shown). Thus, asilicone compound such as silicone resin, or (modified) silicone oil;fluororesin; hexagonal boron nitride; carbon black; and molybdenumdisulfide may be exemplified. A plurality of these friction reducingagents may be used in combination. Because the production method for theelectronic part is conducted in a clean room, it is preferable that asilicone compound or fluororesin is employed. Even among siliconecompounds, a copolymer having silicone macromonomeric units demonstratesa particularly high degree of compatibility with an anti-electrostaticcharge layer, and thus is preferably employed to balance the expansionproperties and the electrostatic charge properties.

It is preferable that an arithmetic mean Ra of a surface of thesubstrate film 106 that is making contact with the die attachment filmof 105 is at least 0.5 μm to no more than 1.5 μm, in order to improvethe peelability between the adhesive sheet 110 and the die attachmentfilm 105.

A mold-release treatment may be performed on a surface of the substratefilm 106 that is making contact with the die attachment film of 105, inorder to allow for the easy peeling between the adhesive sheet 110 andthe die attachment film 105. A mold-release agent such as alkyd resin,silicone resin, fluororesin, unsaturated polyester resin, wax, and thelike, is employed in the mold-release treatment.

The method for forming the adhesive sheet 110 by forming the adhesivelayer 103 on the substrate film 106 is not particularly limited in anymanner. For example, a method of directly coating the adhesive on thesubstrate film 106 via a coater such as a gravure coater, a commacoater, a bar coater, a knife coater, or a roll coater may beexemplified. The adhesive may also be printed on the substrate film 106via relief printing, intaglio printing, lithographic printing,flexographic printing, offset printing, or screen printing.

Although the adhesive sheet 110 may also be used for fixing anelectronic part employed during dicing or during back-grinding, it ispreferable that the die attachment film 105 and the adhesive sheet 110are laminated, and employed as the multi-layered adhesive sheet 100,which is capable of being employed in both a fixing of the electronicpart during a dicing process and an attaching process to the lead frame111.

Die Attachment Film

The die attachment film 105 is composed of an adhesive agent or anadhesive sheet in which an adhesive agent is formed into a film shape.The die attachment film 105 is commercially available as an adhesiveagent or an adhesive laminated on a release film or the like that iscomposed of a PET resin or the like, and the adhesive agent or theadhesive can be transferred to an adherend.

The material of the die attachment film 105 may be any component of anadhesive or adhesive agent that is typically employed. As the adhesive,an epoxy, polyamide, an acrylic, and polyimide may be exemplified. Asthe adhesive agent, an acrylic, vinyl acetate, ethylene-vinyl acetatecopolymer, ethylene-acrylic acid ester copolymer, polyamide,polyethylene, polysulfone, an epoxy, polyimide, polyamide acid,silicone, phenol, rubber polymer, fluororubber polymer, and fluororesinmay be exemplified, with polyimide being preferably employed.

A mixture, a copolymer and a laminate of these components of theadhesive or adhesive agent may be employed in the die attachment film105. An additive, such as a crosslinking promoter, an anti-electrostaticagent, and photopolymerization initiator may also be compounded into thedie attachment film 105, where necessary.

Production Method for Electronic Part

In a production method for the electronic part, a method employing amulti-layered adhesive sheet 100, in which the die attachment film 105is laminated on an adhesive coating surface of the adhesive sheet 110,is preferably employed. The production method for the electronic partemploying the multi-layered adhesive sheet 100 of the present embodimentis not particularly limited in any manner. For example, thebelow-mentioned procedure indicated in FIG. 1 may be exemplified.

(1) The silicon wafer 101 is attached and fixed to the multi-layeredadhesive sheet 100, and the multi-layered adhesive sheet 100 is fixed tothe ring frame 102.

(2) The silicon wafer 101 is diced with the dicing blade 104.

(3) Ultraviolet rays and/or radiation (not shown) are irradiated fromthe substrate film 106 side of the multi-layered adhesive sheet 100, theinterval of the die chip 108 is broadened by radially expanding themulti-layered adhesive sheet 100, and afterwards the die chip 108 ispressed up with a needle or the like (not shown). Next, the die chip 108is suctioned via a vacuum collet or air pincette or the like (notshown), the adhesive sheet 110 and die attachment film 105 are peeledapart, and the die chip 108 having the die attachment film 105 attachedthereto is picked-up.

(4) The die chip 108 having the die attachment film 105 attached theretois mounted on the lead frame 111 or a circuit substrate. Then, the dieattachment film 105 is heated, and the die chip 108 is thermally bondedto the lead frame 111 or a circuit substrate. Finally, the die chip 108mounted on the lead frame 111 or the circuit substrate is molded via aresin (not shown).

A circuit substrate such as one formed of a circuit pattern may beemployed in the present production method instead of the lead frame 111.

The light source of the ultraviolet and/or radiation is not particularlylimited in any manner, and thus any known technology may be employed. Asthe ultraviolet light source, a low-pressure mercury lamp, ahigh-pressure mercury lamp, a ultra-high-pressure mercury lamp, and ametal halide lamp may be exemplified. The radiation to be preferablyemployed is an electron beam, an alpha ray, a beta ray, or a gamma ray.

By irradiating ultraviolet rays and/or radiation, the vinyl groupswithin the molecular compound forming the adhesive layer 103 form athree-dimensional network, and the adhesion of the adhesive layer 103may be reduced. By doing so, superior chip retention may be exhibitedbecause the adhesive layer 103 has high initial adhesion beforeirradiation with the ultraviolet rays and/or radiation; and the dieattachment film 105 and the adhesive layer 103 are easily peeled apart,and the pick-up properties of the die chip 108 may be improved becausethe adhesion of the adhesive layer 103 is reduced after being irradiatedwith ultraviolet rays and/or radiation.

Although the abovementioned embodiment describes that the die attachmentfilm 105 is interposed between the silicon wafer 101 and the adhesivesheet 110, a paste-like adhesive agent may also be employed to replacethe die attachment film 105.

Typically, in cases where employing a paste-like adhesive agent, thepaste-like adhesive agent is applied to the entire rear surface of thesilicon wafer 101, specifically to a circuit non-forming surface forbonding the lead frame 111 or the circuit substrate, this is semi-curedinto a sheet by the heating thereof, and an adhesive semi-cured layerformed. The above-formed adhesive semi-cured layer has the same functionas the abovementioned die attachment film 105. Accordingly, the siliconwafer 101 on which the adhesive semi-cured layer is formed and theadhesive sheet 110 composed of the adhesive layer 103 and the substratefilm 106 are pasted together, so that the adhesive semi-cured layer andthe adhesive layer 103 are in contact, to form a structure identical tothat of FIG. 1(1). Subsequently, similarly to a case where employing thedie attachment film 105, dicing is performed using the dicing blade 104,a die chip having an adhesive semi-cured layer formed thereon ispicked-up, and can be mounted and thermally bonded on the lead frame 111or circuit substrate.

Other than the thermosetting properties of the paste-like adhesiveagent, it is not specifically limited in any particular manner. Forexample, a mixture of one or a plurality of an acrylic, a vinyl acetate,an ethylene-vinyl acetate copolymer, an ethylene-acrylic acid estercopolymer, a polyamide, a polyethylene, polysulfone, an epoxy, apolyimide, a polyamide acid, a silicone, a phenol, a rubber polymer, afluororubber polymer, and a fluororesin may be exemplified.

Effects

Hereinafter, the effects of the multi-layered adhesive sheet 100 of thepresent embodiment will be described with reference to FIG. 1.

As shown in FIG. 1(1), the multi-layered adhesive sheet 100 of thepresent embodiment includes: the substrate film 106, the adhesive layer103 formed by coating the adhesive onto this substrate film 106, and thedie attachment film 105 laminated on top of the adhesive layer 103.

In addition, the abovementioned adhesive layer 103 is composed of anadhesive containing the (meth)acrylic acid ester polymer, the urethaneacrylate oligomer having at least four vinyl groups, and the siliconegraft polymer.

According to the present adhesive, the pick-up operation of the die chip108 shown in FIG. 1(3) may be favorably conducted because the adhesivelayer 103 and the die attachment film 105 are easily peeled apart afterbeing exposed to ultraviolet rays and/or radiation. Moreover, accordingto the above-described adhesive, the peeling of the die chip 108 duringdicing shown in FIG. 1(2) (called “chip scattering”) can be preventedbecause of also being superior in chip retention before exposure toultraviolet rays and/or radiation. Furthermore, according to theabove-described adhesive, the occurrence of poor adhesion viacontaminants when mounting and thermally bonding die chip 108 having thedie attachment film 105 attached thereto on top of the lead frame 111 asshown in FIG. 1(4) can be reduced, because of low contamination of thedie attachment film 105 from a fine adhesive residue.

Moreover, the abovementioned adhesive preferably contains 100 parts bymass of the (meth)acrylic acid ester polymer, at least 20 parts by massto no more than 200 parts by mass of the urethane acrylate oligomerhaving at least four vinyl groups, and at least 0.1 parts by mass to nomore than 10 parts by mass of the silicone graft polymer.

This not only allows for the adhesive sheet 110 and the die attachmentfilm 105 to be easily peeled apart after exposure to ultraviolet raysand/or radiation, but more preferably for the occurrence of a fineresidue generated from a reaction residue or the scooping up of adhesiveduring dicing to be prevented, as well as the peeling of themulti-layered adhesive sheet 110 from the ring frame during dicing to beprevented.

Furthermore, the abovementioned adhesive is preferably a silicone graftpolymer in which a (meth)acrylic acid ester monomer is polymerized asone of the constituent monomers.

In the present case, this is in order to allow for the homogeneity ofthe adhesive.

In addition, when the abovementioned adhesive includes the (meth)acrylicacid ester monomer as one of the constituent monomers, it is preferablethat the (meth)acrylic acid ester monomer contains a hydroxyl group.

Thus, in addition to the adhesive being capable of homogeneity, reactinga hydroxyl group with at least an isocyanate group in a reaction residueof an urethane acrylate oligomer or an isocyanate group in an isocyanatecuring agent, allows for the occurrence of contamination from thesilicon graft polymer to be prevented.

Moreover, it is preferable that the adhesive sheet 110 includes theadhesive layer 103 formed by being coated with the abovementionedadhesive, and more preferably that the adhesive sheet 110 is for fixingan electronic part. Furthermore, it is preferable that the multi-layeredadhesive sheet 100 contains: the adhesive sheet 110, and the dieattachment film 105 laminated on the adhesive layer 103 side of theadhesive sheet 110.

Thus, according to the above-described adhesive sheet 110 ormulti-layered adhesive sheet 100, the pick-up operation of the die chip108 may be favorably conducted because the die attachment film 105 iseasily peeled after being exposed to ultraviolet rays and/or radiation.Moreover, according to the above-described adhesive sheet 110 ormulti-layered adhesive sheet 100, the peeling of the die chip 108 duringdicing can be prevented because it is also superior in chip retentionbefore exposure to ultraviolet rays and/or radiation. Furthermore, theoccurrence of poor adhesion via contaminants when mounting and thermallybonding the die chip 108 having the die attachment film 105 attachedthereto on top of the lead frame 111 because of low contamination(contamination of the die attachment film 105 from the adhesive layer103 is reduced) of the die attachment film 105 from a fine adhesiveresidue.

In addition, a production method for the electronic part may bepreferably employed, which includes: a process of pasting the siliconwafer 101 onto a surface of the die attachment film 105 of theabovementioned multi-layered adhesive sheet 100; a process of performingdicing on the silicon wafer 101 with it pasted to the multi-layeredadhesive sheet 100; and a process of picking-up both the silicon wafer101 and the die attachment film 105 attached to the rear surface of thesilicon wafer 101, by the peeling of the die attachment film 105 fromthe adhesive layer 103 after dicing.

In the present case, because of the exposure (not shown) of theultraviolet rays and/or radiation from the side of the substrate film106 of the multi-layered adhesive sheet 100 after the dicing of thesilicon wafer 101, the die chip 108 can be easily picked-up with the dieattachment film 105 attached to a rear surface of the die chip 108, andthe die chip 108 can be further mounted and bonded as is to the leadframe 111 or the like. In addition, according to the present productionmethod for the electronic part, peeling of the die chip 108 duringdicing (called “chip scattering”) can be prevented because it is alsosuperior in chip retention before exposure to ultraviolet rays and/orradiation. Furthermore, according to the present production method forthe electronic part, because the contamination of the die attachmentfilm 105 from a fine adhesive residue is low, the occurrence of pooradhesion from contamination when the die chip 108 having the dieattachment film 105 attached thereto is mounted and thermally bonded ontop of the lead frame 111 can be prevented.

Moreover, as described with reference to a figure for a DAF usageprocess of FIG. 1, a production method for the electronic part may bepreferably employed, which includes: a process (not shown) of applying apaste-like adhesive agent 105 to the entire rear surface of the siliconwafer 101; a process (not shown) of forming an adhesive semi-cured layer105 by heating the paste-like adhesive agent 105 to semi-cure it into asheet; a process (FIG. 1 (1)) of pasting together the adhesivesemi-cured layer 105 of the silicon wafer 101 and the adhesive layer 103of the adhesive sheet 110; a process (FIG. 1 (2)) of performing dicingon the silicon wafer 101 attached to the adhesive sheet 110; a process(FIG. 1 (3)) of picking-up both the silicon wafer 101 and the adhesivesemi-cured layer 105 attached to a rear surface of the silicon wafer101, by the peeling of the adhesive semi-cured layer 105 from theadhesive layer 103.

In the present case, because of the exposure (not shown) of theultraviolet rays and/or radiation from the side of the substrate film106 of the adhesive sheet 110 after the dicing of the silicon wafer 101,the die chip 108 can be easily picked-up with the adhesive semi-curedlayer 105 attached to a rear surface of the die chip 108, and the diechip 108 can be further mounted and bonded as is to the lead frame 111or the like. Furthermore, according to the present production method forthe electronic part, because the contamination of the adhesivesemi-cured layer 105 from the adhesive layer 103 is low, the occurrenceof poor adhesion from contamination when the die chip 108 having theadhesive semi-cured layer 105 attached thereto is mounted and thermallybonded on top of the lead frame 111 can be prevented.

Although the embodiments of the present invention have been explainedabove with reference to the drawings, these are merely examples, andthus various embodiments other than those mentioned above may also beemployed where necessary.

For example, although the silicon wafer 101 is used as the type of waferin the abovementioned embodiment, any type of wafer may be employed (forexample, a GAN wafer, etc.), without any particular limitations thereon.Regardless of the type of wafer, because the dicing blade 104 exists toproperly cut such a wafer, a processing method for a wafer similar tothat of the abovementioned embodiment is feasible using the dicing blade104, and the effects obtained therefrom similar even in such cases.

EXAMPLES

Hereinafter, the present invention will be described in even greaterdetail via Examples. However, the present invention is not specificallylimited to these Examples.

Preparation of Experimental Materials

The various experimental materials, such as the adhesive, the adhesivesheet, and the multi-layered adhesive sheet were produced by thebelow-mentioned formulation.

1. As the multi-layered adhesive sheet, the following was prepared.

A (meth)acrylic acid ester polymer A: a copolymer of 54% ethyl acrylate,22% butyl acrylate, and 24% methoxy ethyl acrylate, which was obtainedvia suspension polymerization (one of our polymer products).

A (meth)acrylic acid ester polymer B: a copolymer of 95% 2-ethylhexylacrylate, and 5% 2-hydroxy ethyl acrylate, which was obtained viasolution polymerization (one of our polymer products).

Urethane acrylate oligomer A: a terminally-acrylated oligomer, yieldedby reacting the end of a poly(propylene oxide)diol with a trimer of ahexamethylene diisocyanate (aliphatic diisocyanate) to yield aterminally-isocyanated oligomer, and then further reacting theterminally-isocyanated oligomer with a dipentaerythritol pentaacrylate.The urethane acrylate oligomer had 15 functional acrylate groups (15functional groups), and the number average molecular weight (Mn) was3,700 (one of our polymer products).

Urethane acrylate oligomer B: a terminally-acrylated oligomer, yieldedby reacting the end of a poly(propylene oxide)diol with a tolylenediisocyanate (aromatic diisocyanate) to yield a terminally-isocyanatedoligomer, and then further reacting the terminally-isocyanated oligomerwith a dipentaerythritol pentaacrylate. There were 10 functionalacrylate groups (10 functional groups), and the Mn was 3,800 (one of ourpolymer products).

Urethane acrylate oligomer C: a terminally-acrylated oligomer, yieldedby reacting the end of a poly(ethylene oxide)diol with a trimer ofisophorone diisocyanate (alicyclic diisocyanate) to yield aterminally-isocyanated oligomer, and then further reacting theterminally-isocyanated oligomer with a dipentaerythritol pentaacrylate.There were 10 functional acrylate groups (10 functional groups) permolecule, and the Mn was 2,800 (one of our polymer products).

Urethane acrylate oligomer D: a terminally-acrylated oligomer, yieldedby reacting the end of a poly(propylene oxide)diol with a hexamethylenediisocyanate to yield a terminally-isocyanated oligomer, and thenfurther reacting the terminally-isocyanated oligomer with 2-hydroxyethylacrylate. There were two vinyl groups (two functional groups) permolecule, and the number average molecular weight Mn was 3,400 (one ofour polymer products).

Silicone graft polymer A: a silicone graft polymer (one of our polymerproducts), in which a 30 parts by mass of a silicone graft oligomer, 20parts by mass of a butyl acrylate, 30 parts by mass of a methylmethacrylate, and 20 parts by mass 2-hydroxy methylacrylate werepolymerized. As the silicone graft oligomer, a silicone graft oligomer(one of our polymer products) having a methacryloyl group at an end of asilicone molecule chain was employed.

Silicone graft polymer B: a silicone graft polymer (one of our polymerproducts), in which a 30 parts by mass of a silicone graft oligomer, 20parts by mass of a butyl acrylate, 20 parts by mass of a methylmethacrylate, 20 parts by mass of 2-hydroxy methylacrylate, and 10 partsby mass of a methacrylic acid were polymerized, and then furtheraddition-polymerized with glycidyl methacrylate. As the silicone graftoligomer, a silicone graft oligomer (one of our polymer products) havinga methacryloyl group at an end of a silicone molecule chain wasemployed.

Silicone compound A: a silicone oil (product name: KF-96, manufacturedby Shin-Etsu Chemical Corporation).

Photopolymerization initiator: benzyl dimethyl ketal (product name:Irgacure 651, manufactured by Ciba Specialty Chemicals).

Curing agent: 1,6-hexamethylene diisocyanate-trimethylol propane adduct(manufactured by Nippon Polyurethane Industry, Company, Ltd., productname: Colonate HL)

The main components and compounding amount thereof in the adhesivecorresponding to each experimental number are indicated in the Tables 1and 2, and in addition to the components indicated in these Tables,three parts by mass of the photopolymerization initiator and three partsby mass of the curing agent were compounded during the preparation ofeach adhesive. Moreover, the type of compound and the compounding amountthereof are concisely indicated in Tables 1 and 2, for example in a casewhere 100 parts by mass of (meth)acrylic acid ester polymer A wascompounded, “A100” was simply indicated in the corresponding column.Accordingly, for example, the adhesive according to the experimentalnumber 1 includes 100 parts by mass of (meth)acrylic acid ester polymerA, 100 parts by mass of urethane acrylate oligomer A, and one part bymass of silicone graft polymer A, as well as three parts by mass of thephotopolymerization initiator and three parts by mass of the curingagent.

Next, the adhesive was coated on a separator film until a thickness ofthe adhesive layer reached 10 μm after drying, this was then laminatedon a 100 μm PE substrate film to obtain an adhesive sheet. A dieattachment film with a 30 μm thickness was laminated on the adhesivelayer to obtain the multi-layered adhesive sheet.

As a base film, a film including an ionomer resin composed mainly of aZn salt of an ethylene-methacrylic acid-methacrylic acid alkyl estercopolymer, having a melt flow rate (MFR) of 1.5 g/10 min (JIS K7210,210° C.) and a melting point of 96° C., and containing Zn²⁺ ions(product name: Himilan 1650, manufactured by Du Pont-MitsuiPolychemicals Company), was employed.

2. As the die attachment film, the following was prepared.

Die attachment film: a film with a thickness of 30 composed of a mixtureof a polyimide adhesive agent and an epoxy adhesive agent.

3. As the electronic parts assembly, the following was prepared.

In the process for the electronic part, a silicon wafer on which a dummycircuit pattern was formed and having a diameter of six inches and athickness of 0.4 mm was employed.

Dicing Process

The depth of the incision into the adhesive sheet was 30 μm. The dicingwas performed so as to be a chip size of 10 mm×10 mm.The dicing device that was employed was a DAD 341, manufactured by DiscoCorporation. The dicing blade that was employed was anNBC-ZH2050-27HEEE, manufactured by Disco Corporation.Dicing blade shape: an outer diameter of 55.56 mm, a blade thickness of35 μm, and an inner diameter of 19.05 mm.Dicing blade revolution number: 40,000 rpm.Dicing blade feed rate: 80 mm/sec.Cutting water temperature: 25° C.Amount of cutting water: 1.0 L/min.

Expansion Process

After the silicon wafer attached to the multi-layered adhesive sheet wasdiced, expansion was conducted using an expansion device.Expansion device: HS-1800, manufactured by Hugle Electronics,Incorporated.Expansion amount: 20 mm.Expansion speed: 20 mm/sec.Heating conditions: 40° C.×1 min.

Evaluation of Experimental Results

1. Adhesion of the multi-layered adhesive sheet: a multi-layeredadhesive sheet that was preheated to 80° C. was pasted on a siliconwafer, it was pressure bonded by rolling a 2 kg roller back and forthone time. The die attachment film and the adhesive sheet was peeledapart at their interface one day after pressure bonding, using samplesbefore/after they were irradiated with 300 mJ/cm² of ultraviolet rays.The results thereof are indicated in Tables 1 and 2.Peeling method: 180° peel.Tensile speed: 300 mm/min.

2. Chip retention properties: the number of chips retained on themulti-layered adhesive sheet, as indicated in FIG. 2, was evaluated whenthe dicing of the silicon wafers was performed under the abovementionedconditions. The results thereof are indicated in Tables 1 and 2.

⊚ (Superior) At least 95% of the chips were retained on themulti-layered adhesive sheet.◯ (Good) At least 90% to less than 95% of the chips were retained on themulti-layered adhesive sheet.

X (Unacceptable) Less than 90% of the chips were retained on themulti-layered adhesive sheet.

3. Pick-up properties: the silicon wafers were diced and expanded underthe abovementioned conditions, and afterwards the number of chips thatcould be picked-up with the die attachment film attached thereto asindicated in FIG. 3 was evaluated. The results thereof are indicated inTables 1 and 2.

⊚ (Superior) At least 95% of the chips were picked-up.◯ (Good) At least 80% to less than 95% of the chips were picked-up.X (Unacceptable) Less than 80% of the chips were picked-up.

4. Contamination: the adhesive sheet was pasted onto a silicon mirrorwafer, it was irradiated under a high-pressure mercury lamp for 20minutes with 300 mJ/cm² of ultraviolet rays, and afterwards the adhesivesheet was peeled off. The number of residual particles that were atleast 0.28 μm on a pasted upper surface of the silicon mirror wafer(five inches) was measured using a particle counter. The results thereofare indicated in Tables 1 and 2.

⊚ (Excellent) Less than 500 particles.◯ (Good) Less than 2,000 particles.X (Unacceptable) At least 2,000 particles.

TABLE 1 Experimental number 1 2 3 4 5 6 7 8 9 Adhesive (meth)acrylicacid ester A 100 A 100 A 100 A 100 A 100 A 100 A 100 A 100 A 100 layerpolymer (see notes) urethane acrylate A 100 A 10 A 20 A 200 A 250 A 100A 100 A 100 A 100 oligomer silicone graft polymer A 1 A 1 A 1 A 1 A 1 A0.1 A 0.05 A 10 A 20 silicone compound — — — — — — — — — Adhesion withrespect to the die 5.30 4.30 4.80 5.80 5.90 5.85 5.90 2.80 0.80Evaluation attachment film (before UV exposure) N/20 mm with respect tothe die 0.24 0.55 0.45 0.22 0.23 0.44 0.38 0.18 0.18 attachment film(after UV exposure) N/20 mm Evaluation Chip retention properties ⊚ ⊚ ⊚ ⊚⊚ ⊚ ⊚ ⊚ ◯ Pick-up properties ⊚ ◯ ⊚ ⊚ ◯ ⊚ ◯ ⊚ ⊚ Contamination ⊚ ⊚ ⊚ ⊚ ◯ ⊚⊚ ⊚ ◯ Remarks Example Example Example Example Example Example ExampleExample Example Notes: Type and compounding amount (parts by mass)

TABLE 2 Experimental number 1 10 11 12 13 14 15 16 17 Adhesive(meth)acrylic acid A 100 B 100 A 100 A 100 A 100 A 100 A 100 A 100 A 100layer ester polymer (see notes) urethane acrylate A 100 A 100 B 100 C100 D 100 A 100 A 100 — A 100 oligomer silicone graft A 1 A 1 A 1 A 1 A1 B 1 — A 1 — polymer silicone compound — — — — — — A 1 — — Adhesionwith respect to the 5.30 2.70 5.70 5.00 3.30 5.60 3.80 1.10 5.80Evaluation die attachment film (before UV exposure) N/20 mm with respectto the 0.24 0.54 0.33 0.43 5.20 0.18 0.50 1.10 0.80 die attachment film(after UV exposure) N/20 mm Evaluation Chip retention ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ ◯ ◯properties Pick-up properties ⊚ ◯ ◯ ◯ X ⊚ ◯ X X Contamination ⊚ ⊚ ⊚ ⊚ ⊚⊚ X X X Remarks Example Example Example Example Comparative ExampleComparative Comparative Comparative Example Example Example ExampleNotes: Type and compounding amount (parts by mass)

Experimental Discussion

As understood from the experimental results indicated in Tables 1 and 2,the multi-layered adhesive sheet employing the adhesive according to thepresent invention is superior in chip retention properties duringdicing, allows the die attachment film and the adhesive layer to beeasily peeled apart during the pick-up operation, and is also low in itscontamination from fine adhesive residues.

While the present invention has been described with reference to severalparticular embodiments thereof, it is understood that variousmodifications are possible and those skilled in the art would also beable to make such modifications without departing from the true spiritand scope of the invention.

INDUSTRIAL APPLICABILITY

Because a multi-layered adhesive sheet employed in the present inventionachieves the effects of being superior in chip retention during dicing,allowing easy peeling from a chip during a pick-up operation and beinglow in contamination from a fine adhesive residue, it can be preferablyemployed in a production method for an electronic part in which a chipwith a die attachment film layer attached to a rear surface thereof ispicked-up after dicing, and it is mounted and bonded onto the lead frameor the like.

1. An adhesive, comprising: a (meth)acrylic acid ester polymer; aurethane acrylate oligomer having at least four vinyl groups; and asilicone graft polymer.
 2. The adhesive according to claim 1,comprising: at least 20 parts by mass to no more than 200 parts by massof the urethane acrylate oligomer having at least four vinyl groups; andat least 0.1 parts by mass to no more than 10 parts by mass of thesilicone graft polymer, with respect to 100 parts by mass of the(meth)acrylic acid ester polymer.
 3. The adhesive according to claim 1or 2, wherein the silicone graft polymer comprises a (meth)acrylic acidester monomer as one of the prepolymerization compounds.
 4. The adhesiveaccording to claim 3, wherein the (meth)acrylic acid ester monomerincludes a hydroxyl group.
 5. An adhesive sheet, comprising: a substratefilm; and an adhesive layer formed by coating the adhesive of any oneclaims 1 to 4 on the substrate film.
 6. The adhesive sheet according toclaim 5, wherein the adhesive sheet is for fixing an electronic part. 7.A multi-layered adhesive sheet, comprising: the adhesive sheet accordingto claim 6; and a die attachment film laminated on the adhesive layerside of the adhesive sheet.
 8. A production method for an electronicpart obtained by dicing a wafer, comprising the steps of: pasting awafer on a surface of the die attachment film of the multi-layeredadhesive sheet of claim 7; dicing the wafer with it pasted to themulti-layered adhesive sheet; and picking-up both the wafer and the dieattachment film attached to a rear surface of the wafer, by peelingapart the die attachment film and the adhesive layer after the dicing.9. A production method for an electronic part obtained by dicing awafer, comprising the steps of: applying a paste-like adhesive agent toan entire rear surface of the wafer; forming an adhesive semi-curedlayer by heating the paste-like adhesive agent to semi-cure it into asheet; pasting together the adhesive semi-cured layer of the wafer andthe adhesive layer of the adhesive sheet of claim 6; dicing the waferwith it pasted to the adhesive sheet; and picking-up both the wafer andthe adhesive semi-cured layer attached to a rear surface of the wafer,by peeling apart the adhesive semi-cured layer and the adhesive layerafter the dicing.